A useful number........there must be some assumption about the rest of the geometry, though? I am guessing this is for a "long" magnet with flat pole on a semi-infinite substrate??Any assumptions about substrate (obviously ferromagnetic I guess) but does it somehow not matter?I would find this a very useful thing to know but don't understand when to apply it. ThanksThe force of attraction is proportional to the square of the field strength at the face of the electromagnet where it contacts the metal. A field strength of one Tesla has a pull force of 58 pounds per square inch of pole area.